1 Field of the Invention
The present invention relates to a plug and a receptacle for an optical connector that is used for optical transmission.
The invention also relates to an optical connector including such a plug and receptacle.
The invention also relates to electronic equipment having such an optical connector.
2 Description of Related Art
The term “electronic equipment” herein broadly encompasses information communication equipment such as digital TV (television) sets, digital BS (broadcasting satellite) tuners, CS (communication satellite) tuners, DVD (digital versatile disc) players, super audio CD (compact disc) players, AV (audio video) amplifiers, audio, personal computers, personal computer peripheral, portable telephones, and PDA (personal digital assistants); amusement equipment such as pachinko machines and other game equipment; and any other equipment using optical transmission.
A conventional example 1 of a plug and a receptacle of an optical connector is shown in FIGS. 1A through 1C and FIGS. 2A and 2B, which connector (referred to as a rectangular connector) is conforming to RC-5720B, a standard of JEITA (Japan Electronics and Information Technology Industries Association, formerly EIAJ: Electronic Industries Association of Japan). FIG. 1A is a side view of the plug, FIG. 1B is a sectional view of the same, and FIG. 1C is a front view of the same. FIG. 2A is a front view of the receptacle, and FIG. 2B is a sectional side elevation of the same. As shown in FIGS. 1A through 1C, the plug 1001 has a cylindrical plug tip section 1002, a rectangular plug peripheral section 1003, and a plug body 1009 to be held by a person at the time of insertion into the receptacle. On the plug peripheral section 1003 are provided guides 1004 for guiding the plug at the plug insertion and protrusions 1005 for engaging with the receptacle. As shown in FIG. 1B, an optical fiber cable is inserted into a hole 1006 provided at center in the sectional view, and a tip thereof is formed into an optical reference plane 1007 by hot plate processing or polish processing. The plug 1001 is provided with one mechanical reference plane (reference plane for a fit with the receptacle) 1008, and a distance between the optical reference plane 1007 and the mechanical reference plane 1008 is set at 5.4 mm. In FIG. 1C, cross-hatching is provided on the mechanical reference plane 1008 for easy understanding. The receptacle 2001 has an insertion hole 2005 to be associated with the plug peripheral section, an insertion hole 2004 to be associated with the plug tip section, grooves 2006 to be associated with the guides of the plug, a plug tip holding section 2010 for holding the plug tip section, an optical element insertion hole 2008, and holes 2009 to be associated with the protrusions for engaging of the plug, in a rectangular housing 2000. As shown in FIG. 2B, an optical reference plane 2007 is provided at a distance of 9.1 mm from an end surface 2002 of the receptacle 2001, and a mechanical reference plane 2003 is provided at a distance of 5.4 mm from the optical reference plane 2007. The mechanical reference plane 2003 is an end surface of the plug tip holding section 2010.
By the insertion of the plug 1001 into the receptacle 2001, in a structure of this conventional example 1, the mechanical reference plane 1008 provided in the plug 1001 is brought into contact with the mechanical reference plane 2003 provided in the receptacle 2001, so that further insertion is restricted. In a state in which the mechanical reference planes 1008 and 2003 are in contact with each other, the optical reference planes 1007 and 2007 coincide with each other. Thus optical transmission is performed satisfactorily.
A conventional example 2 of a receptacle is shown in FIGS. 3A and 3B (see JP 2002-48952 A, for example). FIG. 3A is a front view in a state with a shutter closed, and FIG. 3B is a front view in a state with a shutter opened. As shown in FIGS. 3A and 3B, the receptacle 3010a has a shutter 3011, a plug insertion hole 3012, and grooves 3017 associated with guides provided on a plug, in a housing 3000. Reference character 3010b denotes a front of the housing of the receptacle. In the receptacle 3010a of the conventional example 2, the plug 1001 of the conventional example 1 can be inserted and fitted into the plug insertion hole 3012. The shutter 3011 opens and closes inside the plug insertion hole 3012 with assistance of a hinge 3016, so that foreign matter can reliably be prevented from entering the plug insertion hole 3012. On a front of the shutter 3011 is provided a groove 3011a for guiding the plug tip section 1007 during the insertion of the plug 1001 of the conventional example 1. As shown in FIG. 3B, blocks 3012a according to a shape of the plug are provided on side surfaces inside the plug insertion hole 3012.
When the plug 1001 of the conventional example 1 is inserted into the plug insertion hole 3012 of the receptacle 3010a of this conventional example 2, an extremity 1011 of the plug peripheral section of the plug 1001 is brought into contact with the blocks 3012a provided in the receptacle 3010a, so that further insertion is restricted. In a state in which the extremity 1011 of the plug peripheral section of the plug 1001 is in contact with the blocks 3012a, optical reference planes of the plug and receptacle coincide with each other.
A conventional example 3 of a receptacle is shown in FIGS. 4A through 4C (see JP 2000-131564 A, for example). FIG. 4A is a front view of the receptacle, FIG. 4B is a side view of the same, and FIG. 4C is a sectional side view of the same. As shown in FIGS. 4A through 4C, the receptacle 4200 has a housing 4205 having an insertion hole 4220 into which a plug is inserted, a shutter 4210 that is mounted on an entrance of the insertion hole 4220 with a hinge structure (having a shaft 4240) and that is intended for generally closing the insertion hole 4220, an elastic body 4230 for biasing the shutter 4210 toward the entrance, and grooves 4221 to be associated with guides provided on the plug. An optical element 4290 is provided behind the insertion hole 4220. When the plug is inserted into the insertion hole 4220, the shutter 4210 is housed in space 4225 in the insertion hole 4220 and functions so as to hold a side surface of the plug.
In the receptacle 4200 of the conventional example 3, a mechanical reference plane is not provided, and it is therefore uncertain which part abuts on the plug when the plug is inserted into the insertion hole 4220.
A conventional example 4 of a plug is a round optical plug 5001 as shown in FIGS. 5A through 5C (e.g., Horizon Tec Co., Ltd., “DIY products, OPB-41, circular plug (for Φ 4.0 mm cord),” online, searched on Jul. 1, 2004, see URL: http://www.horizontec.biz/opb41.htm). FIG. 5A is a side view of the plug 5001, FIG. 5B is a sectional side view of the same, and FIG. 5C is a front view of the same. The plug 5001 has a cylindrical plug tip section 5002, a cylindrical plug peripheral section 5003, and a plug body 5009 to be held by a person on the occasion of insertion into a receptacle. Around the plug peripheral section 5003 is provided an annular protrusion 5004 for engaging with the receptacle. Numeral 5007 denotes a hole in which an optical fiber cable is positioned. The plug 5001, of which the plug peripheral section 5003 is cylindrical, can be inserted into the rectangular receptacle 2001 defined in JEITA RC-5720B at any angle about a center C thereof. Moreover, the plug can be turned after the insertion, and thus torsion of the cable can be canceled.
A positional relation between an optical reference plane 5006 and a mechanical reference plane 5005 in the plug 5001 of the conventional example 4 is the same as the positional relation between the optical reference plane 1007 and the mechanical reference plane 1008 in the rectangular plug 1001 of the conventional example 1.
As apparent from the above, there exist various types of plugs and receptacles, and those plugs and receptacles may be used in combination in various manners.
For example, insertion of the plug 5001 of the conventional example 4 into the receptacle 2001 of the conventional example 1 causes no problem because the optical reference plane 2007 of the receptacle 2001 and the optical reference plane 5006 of the plug 5001 coincide with each other.
When the plug 5001 of the conventional example 4 is inserted into the receptacle 3010a of the conventional example 2, however, the plug 5001 does not rest against the blocks 3012a provided in the receptacle 3010a because a part associated with the extremity 1011 of the plug peripheral section of the plug 1001 of the conventional example 1 is not provided in the plug 5001, but the end surface 3010b of the housing of the receptacle 3010a and an end surface 5008 of the plug body come into contact with each other, so that further insertion of the plug is restricted. In this situation, the optical reference plane 5006 of the plug 5001 is in a position deeper than the optical reference plane 2007 of the receptacle, and contact is therefore made between the plug tip 5006 and an optical element provided inside the receptacle. As a result, the optical element may fail, and flaws on the plug tip 5006 may cause transmission loss and deterioration in transmission quality.
When the plug 5001 of the conventional example 4 is inserted into the receptacle 4200 of the conventional example 3, as is the case with the conventional example 2, the optical element provided inside the receptacle may fail or damage to the plug tip 5006 may cause transmission loss and deterioration in transmission quality because a mechanical reference plane is not provided in the receptacle 4200 of the conventional example 3.